1. A research study examined the blood vitamin D levels of the entire US population of landscape gardeners. The population average level of vitamin D in US landscapers was found to be 37.06 ng/mL with a standard deviation of 4.789 ng/mL. Assuming the true distribution of blood vitamin D levels follows a normal distribution, what is the upper value of the region for which approximately 95% of the data are located within the distribution? Recall the 68-95-99.9% observation discussed in the "Normal Distribution" section of the textbook that is helpful in answering the question.
2. A research study examined the blood vitamin D levels of the entire US population of landscape gardeners. The population average level of vitamin D in US landscapers was found to be 44.25 ng/mL with a standard deviation of 4.461 ng/mL. Assuming the true distribution of blood vitamin D levels follows a normal distribution, if you randomly select a landscaper in the US, what is the likelihood that his/her vitamin D level will be 45.76 ng/mL or less?